1. Field of the Invention
The present invention is directed to apparatus and methods for removing sand and/or other fill material located in a wellbore ahead of a coiled tubing tractor and displacing the material behind the tractor. More particularly, the apparatus and methods of the present invention allow a coiled tubing tractor to drive forward in a wellbore by the removal of fill material in front of the tractor thereby allowing the wheels or traction pads of the tractor to remain in contact with the wellbore.
2. Description of the Related Art
Operators are drilling an increasing number of long reach horizontal wells to better access remote reserves of oil and/or gas. Many of these “extended reach” wells have passed the limit where unaided re-entry to the bottom of the wellbore is possible with practical sizes of coiled tubing. The industry has responded by developing hydraulically powered tractors that can be attached to the bottom of the coiled tubing for the purpose of pulling the coiled tubing along the horizontal section of the well. This technology is relatively new with only a few coiled tubing tractor jobs having been attempted to date but there is concern that the reliability of the technology could be seriously compromised by significant quantities of sand or fill on the low side of the hole. The unanswered question is how reliably can the different tractor types perform when they are trying to drive their wheels or traction pads through a substantial sand bed. Sand beds on the low side of the wellbore represent a potentially significant obstacle. For example, a 3 inch deep sand bed in a 6¼ inch hole could cause a tractor to begin pushing the sand ahead of it until a point is reached where the tool becomes stuck in the wellbore. Thus, there is a need for a way to clear the wellbore of sand or fill in the immediate vicinity ahead of the tractor so the tractor does not have to attempt to negotiate through and/or over such an obstacle. Although sand typically is the most prevalent wellbore fill material, it shall be understood that use of the term “sand” hereinafter shall also include any other wellbore particulates such as drill cuttings, metal shavings and wellbore fines.